The present invention relates to optical disk recording and reproducing.
In Technical Digest of Optical Data Storage, 1991, Vol. 5, lecture no. TUB-3 on pages 112-115 and lecture no. TUB-4 on pages 116-119, there is disclosure of reproducing signals weaker than a reproduction limit. A multi-layer magneto-optical recording film has a layer for "masking " the surrounding information that is on an information recording layer. Since the information (bits) recorded in the information recording layer appear in the portion heated by radiation with a reproducing optical beam, interference between adjacent bits can be suppressed, even if the recording density is high, to improve optical resolution.
In general, an optical disk uses a laser beam for recording and reproducing. Laser disks have been used as the well known compact disk and as external memory for a computer system. To improve the density of recording, it has been proposed to (1) make the laser beam wavelength as short as possible, and (2) provide a mask over the optical disk to shield adjacent recording bits or recording information, thereby to suppress interference with the adjacent recording information.